proxy_pollmgr.c@ 68753

最後變更在這個檔案從68753是 68753,由 vboxsync 提交於 8 年前
Rewrite "channels". Use RTREQQUEUE to schedule requests on the pollmgr thread and just one socket to wake up poll(2). To minimize churn keep the old API, so no other files are affected.
屬性 svn:eol-style 設為 `native` 屬性 svn:keywords 設為 `Id Revision`
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1	/* $Id: proxy_pollmgr.c 68753 2017-09-14 02:15:39Z vboxsync $ */
2	/** @file
3	* NAT Network - poll manager.
4	*/
5
6	/*
7	* Copyright (C) 2013-2016 Oracle Corporation
8	*
9	* This file is part of VirtualBox Open Source Edition (OSE), as
10	* available from http://www.alldomusa.eu.org. This file is free software;
11	* you can redistribute it and/or modify it under the terms of the GNU
12	* General Public License (GPL) as published by the Free Software
13	* Foundation, in version 2 as it comes in the "COPYING" file of the
14	* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15	* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16	*/
17
18	#define LOG_GROUP LOG_GROUP_NAT_SERVICE
19
20	#include "winutils.h"
21
22	#include "proxy_pollmgr.h"
23	#include "proxy.h"
24
25	#ifndef RT_OS_WINDOWS
26	#include <sys/socket.h>
27	#include <netinet/in.h>
28	#include <err.h>
29	#include <errno.h>
30	#include <fcntl.h>
31	#include <poll.h>
32	#include <stdio.h>
33	#include <stdlib.h>
34	#include <string.h>
35	#include <time.h>
36	#include <unistd.h>
37	#else
38	#include <iprt/err.h>
39	#include <stdlib.h>
40	#include <string.h>
41	#include "winpoll.h"
42	#endif
43
44	#include <iprt/req.h>
45	#include <iprt/err.h>
46
47
48	#define POLLMGR_GARBAGE (-1)
49
50
51	enum {
52	POLLMGR_QUEUE = 0,
53
54	POLLMGR_SLOT_STATIC_COUNT,
55	POLLMGR_SLOT_FIRST_DYNAMIC = POLLMGR_SLOT_STATIC_COUNT
56	};
57
58
59	struct pollmgr_chan {
60	struct pollmgr_handler *handler;
61	void *arg;
62	bool arg_valid;
63	};
64
65	struct pollmgr {
66	struct pollfd *fds;
67	struct pollmgr_handler **handlers;
68	nfds_t capacity; /* allocated size of the arrays */
69	nfds_t nfds; /* part of the arrays in use */
70
71	/* channels (socketpair) for static slots */
72	SOCKET chan[POLLMGR_SLOT_STATIC_COUNT][2];
73	#define POLLMGR_CHFD_RD 0 /* - pollmgr side */
74	#define POLLMGR_CHFD_WR 1 /* - client side */
75
76
77	/* emulate channels with request queue */
78	RTREQQUEUE queue;
79	struct pollmgr_handler queue_handler;
80	struct pollmgr_chan chan_handlers[POLLMGR_CHAN_COUNT];
81	} pollmgr;
82
83
84	static int pollmgr_queue_callback(struct pollmgr_handler *, SOCKET, int);
85	static void pollmgr_chan_call_handler(int, void *);
86
87	static void pollmgr_loop(void);
88
89	static void pollmgr_add_at(int, struct pollmgr_handler *, SOCKET, int);
90	static void pollmgr_refptr_delete(struct pollmgr_refptr *);
91
92
93	/*
94	* We cannot portably peek at the length of the incoming datagram and
95	* pre-allocate pbuf chain to recvmsg() directly to it. On Linux it's
96	* possible to recv with MSG_PEEK\|MSG_TRUC, but extra syscall is
97	* probably more expensive (haven't measured) than doing an extra copy
98	* of data, since typical UDP datagrams are small enough to avoid
99	* fragmentation.
100	*
101	* We can use shared buffer here since we read from sockets
102	* sequentially in a loop over pollfd.
103	*/
104	u8_t pollmgr_udpbuf[64 * 1024];
105
106
107	int
108	pollmgr_init(void)
109	{
110	struct pollfd *newfds;
111	struct pollmgr_handler **newhdls;
112	nfds_t newcap;
113	int rc, status;
114	nfds_t i;
115
116	rc = RTReqQueueCreate(&pollmgr.queue);
117	if (RT_FAILURE(rc))
118	return -1;
119
120	pollmgr.fds = NULL;
121	pollmgr.handlers = NULL;
122	pollmgr.capacity = 0;
123	pollmgr.nfds = 0;
124
125	for (i = 0; i < POLLMGR_SLOT_STATIC_COUNT; ++i) {
126	pollmgr.chan[i][POLLMGR_CHFD_RD] = INVALID_SOCKET;
127	pollmgr.chan[i][POLLMGR_CHFD_WR] = INVALID_SOCKET;
128	}
129
130	for (i = 0; i < POLLMGR_SLOT_STATIC_COUNT; ++i) {
131	#ifndef RT_OS_WINDOWS
132	int j;
133
134	status = socketpair(PF_LOCAL, SOCK_DGRAM, 0, pollmgr.chan[i]);
135	if (status < 0) {
136	DPRINTF(("socketpair: %R[sockerr]\n", SOCKERRNO()));
137	goto cleanup_close;
138	}
139
140	/* now manually make them O_NONBLOCK */
141	for (j = 0; j < 2; ++j) {
142	int s = pollmgr.chan[i][j];
143	int sflags;
144
145	sflags = fcntl(s, F_GETFL, 0);
146	if (sflags < 0) {
147	DPRINTF0(("F_GETFL: %R[sockerr]\n", errno));
148	goto cleanup_close;
149	}
150
151	status = fcntl(s, F_SETFL, sflags \| O_NONBLOCK);
152	if (status < 0) {
153	DPRINTF0(("O_NONBLOCK: %R[sockerr]\n", errno));
154	goto cleanup_close;
155	}
156	}
157	#else
158	status = RTWinSocketPair(PF_INET, SOCK_DGRAM, 0, pollmgr.chan[i]);
159	if (RT_FAILURE(status)) {
160	goto cleanup_close;
161	}
162	#endif
163	}
164
165
166	newcap = 16; /* XXX: magic */
167	LWIP_ASSERT1(newcap >= POLLMGR_SLOT_STATIC_COUNT);
168
169	newfds = (struct pollfd *)
170	malloc(newcap * sizeof(*pollmgr.fds));
171	if (newfds == NULL) {
172	DPRINTF(("%s: Failed to allocate fds array\n", __func__));
173	goto cleanup_close;
174	}
175
176	newhdls = (struct pollmgr_handler **)
177	malloc(newcap * sizeof(*pollmgr.handlers));
178	if (newhdls == NULL) {
179	DPRINTF(("%s: Failed to allocate handlers array\n", __func__));
180	free(newfds);
181	goto cleanup_close;
182	}
183
184	pollmgr.capacity = newcap;
185	pollmgr.fds = newfds;
186	pollmgr.handlers = newhdls;
187
188	pollmgr.nfds = POLLMGR_SLOT_STATIC_COUNT;
189
190	for (i = 0; i < pollmgr.capacity; ++i) {
191	pollmgr.fds[i].fd = INVALID_SOCKET;
192	pollmgr.fds[i].events = 0;
193	pollmgr.fds[i].revents = 0;
194	}
195
196	/* add request queue notification */
197	pollmgr.queue_handler.callback = pollmgr_queue_callback;
198	pollmgr.queue_handler.data = NULL;
199	pollmgr.queue_handler.slot = -1;
200
201	pollmgr_add_at(POLLMGR_QUEUE, &pollmgr.queue_handler,
202	pollmgr.chan[POLLMGR_QUEUE][POLLMGR_CHFD_RD],
203	POLLIN);
204
205	return 0;
206
207	cleanup_close:
208	for (i = 0; i < POLLMGR_SLOT_STATIC_COUNT; ++i) {
209	SOCKET *chan = pollmgr.chan[i];
210	if (chan[POLLMGR_CHFD_RD] != INVALID_SOCKET) {
211	closesocket(chan[POLLMGR_CHFD_RD]);
212	closesocket(chan[POLLMGR_CHFD_WR]);
213	}
214	}
215
216	return -1;
217	}
218
219
220	/*
221	* Add new channel. We now implement channels with request queue, so
222	* all channels get the same socket that triggers queue processing.
223	*
224	* Must be called before pollmgr loop is started, so no locking.
225	*/
226	SOCKET
227	pollmgr_add_chan(int slot, struct pollmgr_handler *handler)
228	{
229	AssertReturn(0 <= slot && slot < POLLMGR_CHAN_COUNT, INVALID_SOCKET);
230	AssertReturn(handler != NULL && handler->callback != NULL, INVALID_SOCKET);
231
232	handler->slot = slot;
233	pollmgr.chan_handlers[slot].handler = handler;
234	return pollmgr.chan[POLLMGR_QUEUE][POLLMGR_CHFD_WR];
235	}
236
237
238	/*
239	* This used to actually send data over the channel's socket. Now we
240	* queue a request and send single byte notification over shared
241	* POLLMGR_QUEUE socket.
242	*/
243	ssize_t
244	pollmgr_chan_send(int slot, void *buf, size_t nbytes)
245	{
246	static const char notification = 0x5a;
247
248	void *ptr;
249	SOCKET fd;
250	ssize_t nsent;
251	int rc;
252
253	AssertReturn(0 <= slot && slot < POLLMGR_CHAN_COUNT, -1);
254
255	/*
256	* XXX: Hack alert. We only ever "sent" single pointer which was
257	* simultaneously both the wakeup event for the poll and the
258	* argument for the channel handler that it read from the channel.
259	* So now we pass this pointer to the request and arrange for the
260	* handler to "read" it when it asks for it.
261	*/
262	if (nbytes != sizeof(void *)) {
263	return -1;
264	}
265
266	ptr = (void *)buf;
267
268	rc = RTReqQueueCallEx(pollmgr.queue, NULL, 0,
269	RTREQFLAGS_VOID \| RTREQFLAGS_NO_WAIT,
270	(PFNRT)pollmgr_chan_call_handler, 2,
271	slot, ptr);
272
273	fd = pollmgr.chan[POLLMGR_QUEUE][POLLMGR_CHFD_WR];
274	nsent = send(fd, &notification, 1, 0);
275	if (nsent == SOCKET_ERROR) {
276	DPRINTF(("send on chan %d: %R[sockerr]\n", slot, SOCKERRNO()));
277	return -1;
278	}
279	else if ((size_t)nsent != 1) {
280	DPRINTF(("send on chan %d: datagram truncated to %u bytes",
281	slot, (unsigned int)nsent));
282	return -1;
283	}
284
285	/* caller thinks it's sending the pointer */
286	return sizeof(void *);
287	}
288
289
290	/*
291	* pollmgr_chan_send() sent us a notification, process the queue.
292	*/
293	static int
294	pollmgr_queue_callback(struct pollmgr_handler *handler, SOCKET fd, int revents)
295	{
296	ssize_t nread;
297	int sockerr;
298	int rc;
299
300	RT_NOREF(handler, revents);
301	Assert(pollmgr.queue != NIL_RTREQQUEUE);
302
303	nread = recv(fd, (char *)pollmgr_udpbuf, sizeof(pollmgr_udpbuf), 0);
304	sockerr = SOCKERRNO(); /* save now, may be clobbered */
305
306	if (nread == SOCKET_ERROR) {
307	DPRINTF0(("%s: recv: %R[sockerr]\n", __func__, sockerr));
308	return POLLIN;
309	}
310
311	DPRINTF2(("%s: read %zd\n", __func__, nread));
312	if (nread == 0) {
313	return POLLIN;
314	}
315
316	rc = RTReqQueueProcess(pollmgr.queue, 0);
317	if (RT_UNLIKELY(rc != VERR_TIMEOUT && RT_FAILURE_NP(rc))) {
318	DPRINTF0(("%s: RTReqQueueProcess: %Rrc\n", __func__, rc));
319	}
320
321	return POLLIN;
322	}
323
324
325	/*
326	* Queued requests use this function to emulate the call to the
327	* handler's callback.
328	*/
329	static void
330	pollmgr_chan_call_handler(int slot, void *arg)
331	{
332	struct pollmgr_handler *handler;
333	int nevents;
334
335	AssertReturnVoid(0 <= slot && slot < POLLMGR_CHAN_COUNT);
336
337	handler = pollmgr.chan_handlers[slot].handler;
338	AssertReturnVoid(handler != NULL && handler->callback != NULL);
339
340	/* arrange for pollmgr_chan_recv_ptr() to "receive" the arg */
341	pollmgr.chan_handlers[slot].arg = arg;
342	pollmgr.chan_handlers[slot].arg_valid = true;
343
344	nevents = handler->callback(handler, -1, POLLIN);
345	if (nevents != POLLIN) {
346	DPRINTF2(("%s: nevents=0x%x!\n", nevents));
347	}
348	}
349
350
351	/*
352	* "Receive" a pointer "sent" over poll manager channel.
353	*/
354	void *
355	pollmgr_chan_recv_ptr(struct pollmgr_handler *handler, SOCKET fd, int revents)
356	{
357	int slot;
358	void *ptr;
359
360	RT_NOREF(fd);
361
362	slot = handler->slot;
363	Assert(0 <= slot && slot < POLLMGR_CHAN_COUNT);
364
365	if (revents & POLLNVAL) {
366	errx(EXIT_FAILURE, "chan %d: fd invalid", (int)handler->slot);
367	/* NOTREACHED */
368	}
369
370	if (revents & (POLLERR \| POLLHUP)) {
371	errx(EXIT_FAILURE, "chan %d: fd error", (int)handler->slot);
372	/* NOTREACHED */
373	}
374
375	LWIP_ASSERT1(revents & POLLIN);
376
377	if (!pollmgr.chan_handlers[slot].arg_valid) {
378	err(EXIT_FAILURE, "chan %d: recv", (int)handler->slot);
379	/* NOTREACHED */
380	}
381
382	ptr = pollmgr.chan_handlers[slot].arg;
383	pollmgr.chan_handlers[slot].arg_valid = false;
384
385	return ptr;
386	}
387
388
389	/*
390	* Must be called from pollmgr loop (via callbacks), so no locking.
391	*/
392	int
393	pollmgr_add(struct pollmgr_handler *handler, SOCKET fd, int events)
394	{
395	int slot;
396
397	DPRINTF2(("%s: new fd %d\n", __func__, fd));
398
399	if (pollmgr.nfds == pollmgr.capacity) {
400	struct pollfd *newfds;
401	struct pollmgr_handler **newhdls;
402	nfds_t newcap;
403	nfds_t i;
404
405	newcap = pollmgr.capacity * 2;
406
407	newfds = (struct pollfd *)
408	realloc(pollmgr.fds, newcap * sizeof(*pollmgr.fds));
409	if (newfds == NULL) {
410	DPRINTF(("%s: Failed to reallocate fds array\n", __func__));
411	handler->slot = -1;
412	return -1;
413	}
414
415	pollmgr.fds = newfds; /* don't crash/leak if realloc(handlers) fails */
416	/* but don't update capacity yet! */
417
418	newhdls = (struct pollmgr_handler **)
419	realloc(pollmgr.handlers, newcap * sizeof(*pollmgr.handlers));
420	if (newhdls == NULL) {
421	DPRINTF(("%s: Failed to reallocate handlers array\n", __func__));
422	/* if we failed to realloc here, then fds points to the
423	* new array, but we pretend we still has old capacity */
424	handler->slot = -1;
425	return -1;
426	}
427
428	pollmgr.handlers = newhdls;
429	pollmgr.capacity = newcap;
430
431	for (i = pollmgr.nfds; i < newcap; ++i) {
432	newfds[i].fd = INVALID_SOCKET;
433	newfds[i].events = 0;
434	newfds[i].revents = 0;
435	newhdls[i] = NULL;
436	}
437	}
438
439	slot = pollmgr.nfds;
440	++pollmgr.nfds;
441
442	pollmgr_add_at(slot, handler, fd, events);
443	return slot;
444	}
445
446
447	static void
448	pollmgr_add_at(int slot, struct pollmgr_handler *handler, SOCKET fd, int events)
449	{
450	pollmgr.fds[slot].fd = fd;
451	pollmgr.fds[slot].events = events;
452	pollmgr.fds[slot].revents = 0;
453	pollmgr.handlers[slot] = handler;
454
455	handler->slot = slot;
456	}
457
458
459	void
460	pollmgr_update_events(int slot, int events)
461	{
462	LWIP_ASSERT1(slot >= POLLMGR_SLOT_FIRST_DYNAMIC);
463	LWIP_ASSERT1((nfds_t)slot < pollmgr.nfds);
464
465	pollmgr.fds[slot].events = events;
466	}
467
468
469	void
470	pollmgr_del_slot(int slot)
471	{
472	LWIP_ASSERT1(slot >= POLLMGR_SLOT_FIRST_DYNAMIC);
473
474	DPRINTF2(("%s(%d): fd %d ! DELETED\n",
475	__func__, slot, pollmgr.fds[slot].fd));
476
477	pollmgr.fds[slot].fd = INVALID_SOCKET; /* see poll loop */
478	}
479
480
481	void
482	pollmgr_thread(void *ignored)
483	{
484	LWIP_UNUSED_ARG(ignored);
485	pollmgr_loop();
486	}
487
488
489	static void
490	pollmgr_loop(void)
491	{
492	int nready;
493	SOCKET delfirst;
494	SOCKET *pdelprev;
495	int i;
496
497	for (;;) {
498	#ifndef RT_OS_WINDOWS
499	nready = poll(pollmgr.fds, pollmgr.nfds, -1);
500	#else
501	int rc = RTWinPoll(pollmgr.fds, pollmgr.nfds,RT_INDEFINITE_WAIT, &nready);
502	if (RT_FAILURE(rc)) {
503	err(EXIT_FAILURE, "poll"); /* XXX: what to do on error? */
504	/* NOTREACHED*/
505	}
506	#endif
507
508	DPRINTF2(("%s: ready %d fd%s\n",
509	__func__, nready, (nready == 1 ? "" : "s")));
510
511	if (nready < 0) {
512	if (errno == EINTR) {
513	continue;
514	}
515
516	err(EXIT_FAILURE, "poll"); /* XXX: what to do on error? */
517	/* NOTREACHED*/
518	}
519	else if (nready == 0) { /* cannot happen, we wait forever (-1) */
520	continue; /* - but be defensive */
521	}
522
523
524	delfirst = INVALID_SOCKET;
525	pdelprev = &delfirst;
526
527	for (i = 0; (nfds_t)i < pollmgr.nfds && nready > 0; ++i) {
528	struct pollmgr_handler *handler;
529	SOCKET fd;
530	int revents, nevents;
531
532	fd = pollmgr.fds[i].fd;
533	revents = pollmgr.fds[i].revents;
534
535	/*
536	* Channel handlers can request deletion of dynamic slots
537	* by calling pollmgr_del_slot() that clobbers slot's fd.
538	*/
539	if (fd == INVALID_SOCKET && i >= POLLMGR_SLOT_FIRST_DYNAMIC) {
540	/* adjust count if events were pending for that slot */
541	if (revents != 0) {
542	--nready;
543	}
544
545	/* pretend that slot handler requested deletion */
546	nevents = -1;
547	goto update_events;
548	}
549
550	if (revents == 0) {
551	continue; /* next fd */
552	}
553	--nready;
554
555	handler = pollmgr.handlers[i];
556
557	if (handler != NULL && handler->callback != NULL) {
558	#ifdef LWIP_PROXY_DEBUG
559	# if LWIP_PROXY_DEBUG /* DEBUG */
560	if (i < POLLMGR_SLOT_FIRST_DYNAMIC) {
561	if (revents == POLLIN) {
562	DPRINTF2(("%s: ch %d\n", __func__, i));
563	}
564	else {
565	DPRINTF2(("%s: ch %d @ revents 0x%x!\n",
566	__func__, i, revents));
567	}
568	}
569	else {
570	DPRINTF2(("%s: fd %d @ revents 0x%x\n",
571	__func__, fd, revents));
572	}
573	# endif /* LWIP_PROXY_DEBUG / DEBUG */
574	#endif
575	nevents = (*handler->callback)(handler, fd, revents);
576	}
577	else {
578	DPRINTF0(("%s: invalid handler for fd %d: ", __func__, fd));
579	if (handler == NULL) {
580	DPRINTF0(("NULL\n"));
581	}
582	else {
583	DPRINTF0(("%p (callback = NULL)\n", (void *)handler));
584	}
585	nevents = -1; /* delete it */
586	}
587
588	update_events:
589	if (nevents >= 0) {
590	if (nevents != pollmgr.fds[i].events) {
591	DPRINTF2(("%s: fd %d ! nevents 0x%x\n",
592	__func__, fd, nevents));
593	}
594	pollmgr.fds[i].events = nevents;
595	}
596	else if (i < POLLMGR_SLOT_FIRST_DYNAMIC) {
597	/* Don't garbage-collect channels. */
598	DPRINTF2(("%s: fd %d ! DELETED (channel %d)\n",
599	__func__, fd, i));
600	pollmgr.fds[i].fd = INVALID_SOCKET;
601	pollmgr.fds[i].events = 0;
602	pollmgr.fds[i].revents = 0;
603	pollmgr.handlers[i] = NULL;
604	}
605	else {
606	DPRINTF2(("%s: fd %d ! DELETED\n", __func__, fd));
607
608	/* schedule for deletion (see g/c loop for details) */
609	pdelprev = i; / make previous entry point to us */
610	pdelprev = &pollmgr.fds[i].fd;
611
612	pollmgr.fds[i].fd = INVALID_SOCKET; /* end of list (for now) */
613	pollmgr.fds[i].events = POLLMGR_GARBAGE;
614	pollmgr.fds[i].revents = 0;
615	pollmgr.handlers[i] = NULL;
616	}
617	} /* processing loop */
618
619
620	/*
621	* Garbage collect and compact the array.
622	*
623	* We overload pollfd::fd of garbage entries to store the
624	* index of the next garbage entry. The garbage list is
625	* co-directional with the fds array. The index of the first
626	* entry is in "delfirst", the last entry "points to"
627	* INVALID_SOCKET.
628	*
629	* See update_events code for nevents < 0 at the end of the
630	* processing loop above.
631	*/
632	while (delfirst != INVALID_SOCKET) {
633	const int last = pollmgr.nfds - 1;
634
635	/*
636	* We want a live entry in the last slot to swap into the
637	* freed slot, so make sure we have one.
638	*/
639	if (pollmgr.fds[last].events == POLLMGR_GARBAGE /* garbage */
640	\|\| pollmgr.fds[last].fd == INVALID_SOCKET) /* or killed */
641	{
642	/* drop garbage entry at the end of the array */
643	--pollmgr.nfds;
644
645	if (delfirst == (SOCKET)last) {
646	/* congruent to delnext >= pollmgr.nfds test below */
647	delfirst = INVALID_SOCKET; /* done */
648	}
649	}
650	else {
651	const SOCKET delnext = pollmgr.fds[delfirst].fd;
652
653	/* copy live entry at the end to the first slot being freed */
654	pollmgr.fds[delfirst] = pollmgr.fds[last]; /* struct copy */
655	pollmgr.handlers[delfirst] = pollmgr.handlers[last];
656	pollmgr.handlers[delfirst]->slot = (int)delfirst;
657	--pollmgr.nfds;
658
659	if ((nfds_t)delnext >= pollmgr.nfds) {
660	delfirst = INVALID_SOCKET; /* done */
661	}
662	else {
663	delfirst = delnext;
664	}
665	}
666
667	pollmgr.fds[last].fd = INVALID_SOCKET;
668	pollmgr.fds[last].events = 0;
669	pollmgr.fds[last].revents = 0;
670	pollmgr.handlers[last] = NULL;
671	}
672	} /* poll loop */
673	}
674
675
676	/**
677	* Create strongly held refptr.
678	*/
679	struct pollmgr_refptr *
680	pollmgr_refptr_create(struct pollmgr_handler *ptr)
681	{
682	struct pollmgr_refptr *rp;
683
684	LWIP_ASSERT1(ptr != NULL);
685
686	rp = (struct pollmgr_refptr )malloc(sizeof (rp));
687	if (rp == NULL) {
688	return NULL;
689	}
690
691	sys_mutex_new(&rp->lock);
692	rp->ptr = ptr;
693	rp->strong = 1;
694	rp->weak = 0;
695
696	return rp;
697	}
698
699
700	static void
701	pollmgr_refptr_delete(struct pollmgr_refptr *rp)
702	{
703	if (rp == NULL) {
704	return;
705	}
706
707	LWIP_ASSERT1(rp->strong == 0);
708	LWIP_ASSERT1(rp->weak == 0);
709
710	sys_mutex_free(&rp->lock);
711	free(rp);
712	}
713
714
715	/**
716	* Add weak reference before "rp" is sent over a poll manager channel.
717	*/
718	void
719	pollmgr_refptr_weak_ref(struct pollmgr_refptr *rp)
720	{
721	sys_mutex_lock(&rp->lock);
722
723	LWIP_ASSERT1(rp->ptr != NULL);
724	LWIP_ASSERT1(rp->strong > 0);
725
726	++rp->weak;
727
728	sys_mutex_unlock(&rp->lock);
729	}
730
731
732	/**
733	* Try to get the pointer from implicitely weak reference we've got
734	* from a channel.
735	*
736	* If we detect that the object is still strongly referenced, but no
737	* longer registered with the poll manager we abort strengthening
738	* conversion here b/c lwip thread callback is already scheduled to
739	* destruct the object.
740	*/
741	struct pollmgr_handler *
742	pollmgr_refptr_get(struct pollmgr_refptr *rp)
743	{
744	struct pollmgr_handler *handler;
745	size_t weak;
746
747	sys_mutex_lock(&rp->lock);
748
749	LWIP_ASSERT1(rp->weak > 0);
750	weak = --rp->weak;
751
752	handler = rp->ptr;
753	if (handler == NULL) {
754	LWIP_ASSERT1(rp->strong == 0);
755	sys_mutex_unlock(&rp->lock);
756	if (weak == 0) {
757	pollmgr_refptr_delete(rp);
758	}
759	return NULL;
760	}
761
762	LWIP_ASSERT1(rp->strong == 1);
763
764	/*
765	* Here we woild do:
766	*
767	* ++rp->strong;
768	*
769	* and then, after channel handler is done, we would decrement it
770	* back.
771	*
772	* Instead we check that the object is still registered with poll
773	* manager. If it is, there's no race with lwip thread trying to
774	* drop its strong reference, as lwip thread callback to destruct
775	* the object is always scheduled by its poll manager callback.
776	*
777	* Conversly, if we detect that the object is no longer registered
778	* with poll manager, we immediately abort. Since channel handler
779	* can't do anything useful anyway and would have to return
780	* immediately.
781	*
782	* Since channel handler would always find rp->strong as it had
783	* left it, just elide extra strong reference creation to avoid
784	* the whole back-and-forth.
785	*/
786
787	if (handler->slot < 0) { /* no longer polling */
788	sys_mutex_unlock(&rp->lock);
789	return NULL;
790	}
791
792	sys_mutex_unlock(&rp->lock);
793	return handler;
794	}
795
796
797	/**
798	* Remove (the only) strong reference.
799	*
800	* If it were real strong/weak pointers, we should also call
801	* destructor for the referenced object, but
802	*/
803	void
804	pollmgr_refptr_unref(struct pollmgr_refptr *rp)
805	{
806	sys_mutex_lock(&rp->lock);
807
808	LWIP_ASSERT1(rp->strong == 1);
809	--rp->strong;
810
811	if (rp->strong > 0) {
812	sys_mutex_unlock(&rp->lock);
813	}
814	else {
815	size_t weak;
816
817	/* void ptr = rp->ptr; /
818	rp->ptr = NULL;
819
820	/* delete ptr; // see doc comment */
821
822	weak = rp->weak;
823	sys_mutex_unlock(&rp->lock);
824	if (weak == 0) {
825	pollmgr_refptr_delete(rp);
826	}
827	}
828	}

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source: vbox/trunk/src/VBox/NetworkServices/NAT/proxy_pollmgr.c@ 68753

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